Automated apparatus and methods for fluid analysis, such as hematologic analysis, typically pump a sample containing the particles suspended in a dispersion through a particle analyzer which detects differences in electrical, optical, chemical or other characteristics of the particles, and generates signals having characteristics relating to the differences. The signals are in turn transmitted to a processor for determining the parameters of the particle distributions.
Automated hematologic analysis typically involves mixing within a cuvette or other mixing vessel a whole blood sample with several reagent-mixture components, such as diluent, to create a reagent mixture which facilitates cell discrimination and identification. The reagent mixture is then pumped from the cuvette through a particle analyzer which detects the size (volume) and/or opacity of the blood cells by electrical or optical differences. The blood cells are detected or counted for a period of time sufficient to gather data for analysis, and data points are then stored and analyzed in a processor. The data may then be displayed in the form of a two-dimensional or three-dimensional histogram.
As a result of the reagent-mixing process in the cuvette or other mixing vessel and other inefficiencies in fluid transportation, prior art apparatus for hematologic and other fluid analyses generally use a substantially greater volume of blood or other sample fluid than the particle analyzers require for complete analysis. Accordingly, a substantial portion of the samples are typically discarded as waste. These inefficiencies lead to additional costs and inconvenience.
In addition, the mixing cuvette or other mixing vessel and related fluid-handling components, such as fluid conduits, valves, etc., require gravity and/or a controlled ambient pressure to mix the various reagent-mixture components, thus preventing the use of such apparatus in gravity-free applications and on moving vehicles, such as submarines, airplanes, ships, and land-based vehicles.
Moreover, once a reagent-mixture is made in a mixing cuvette or other mixing vessel, the mixture typically cannot be changed. Thus, for example, if a blood-cell abnormality is detected and it is necessary to change the dilution or mixture ratio of the reagent mixture to further assess the abnormality, the original reagent mixture must be discarded and another sample batch prepared, thus leading to sample waste, inconvenience and delays in obtaining analysis results.
In hematologic analysis, when the reagent-mixture components are combined in a mixing cuvette or other mixing vessel with lytic reagents, they are generally not immediately uniformly distributed to the blood cells. For example, there is typically a higher concentration of lytic reagents in the portion of the cuvette or vessel where the reagents are introduced. As a result, the lytic reagents have a varying effect on the blood cells throughout the sample batch and, accordingly, certain cells receive a higher gradient of lytic shock than do others. This uneven gradient of lytic shock typically results in insufficient separation in the blood cells under-exposed to lytic reagents, and damage and possible destruction of cells over-exposed to lytic reagents.
It is an object of the present invention to overcome the drawbacks and disadvantages of prior art apparatus and methods for fluid and/or particle analysis.